It is known to control pressure in a wellbore by controlling a level of pressure applied to the wellbore at or near the surface. This applied pressure can be from one or more of a variety of sources, such as, backpressure applied by a choke in a mud return line, pressure applied by a dedicated backpressure pump, and/or pressure diverted from a standpipe line to the mud return line.
Therefore, it will be appreciated that improvements are continually needed in the art of controlling pressure in drilling operations.